Normal Values for High-Resolution Anorectal Manometry in Healthy Women: Effects of Age and Significance of Rectoanal Gradient

Abstract

Background and Aims High-resolution manometry (HRM) is used to measure anal pressures in clinical practice but normal values have not been available. While rectal evacuation is assessed by the rectoanal gradient during simulated evacuation, there is substantial overlap between healthy people and defecatory disorders, and the effects of age are unknown. We evaluated the effects of age on anorectal pressures and rectal balloon expulsion in healthy women. Design Anorectal pressures (HRM), rectal sensation, and balloon expulsion time (BET) were evaluated in 62 asymptomatic women ranging in age from 21 to 80 years (median age 44 years) without risk factors for anorectal trauma. Thirty women were aged less than 50 years. Results Age is associated with lower (r = − 0.47, p < 0.01) anal resting [63[5] (≥50 y), 88[3] (<50 y)] but not squeeze pressures; higher rectal pressure and rectoanal gradient during simulated evacuation (r = 0.3, p < 0.05); and a shorter (r = −0.4, p < 0.01) rectal BET [17[9]s (≥50 y) vs 31[10]s (<50 y)]. Only 5 women had a prolonged (> 60 s) rectal BET but 52 had higher anal than rectal pressures (ie, negative gradient) during simulated evacuation. The gradient was more negative in younger (−41[6] mm Hg) than older (−12[6] mm Hg) women and negatively (r = −0.51, p <0.0001) correlated with rectal BET but only explained 16% of the variation in rectal BET. Conclusions These observations provide normal values for anorectal pressures by HRM. Increasing age is associated with lower anal resting pressure, a more positive rectoanal gradient during simulated evacuation, and a shorter BET in asymptomatic women. While the rectoanal gradient is negatively correlated with rectal BET, this gradient is negative even in a majority of asymptomatic women, undermining the utility of a negative gradient for diagnosing defecatory disorders by HRM.

How to Perform and Interpret a High-resolution Anorectal Manometry Test

“…24,27 Increasing age is associated with a lower anal resting pressure. 22,23,27 Interestingly, anal resting pressure in healthy women was lower in a study from Korea 24 than in different studies from the United States and Europe. 7,22,26 These differences are more likely explained by differences in techniques rather than ethnic differences because anal pressures in healthy Asian volunteers 23,25 were similar to those from a group that included participants from Western countries.…”

“…22,23,27 Interestingly, anal resting pressure in healthy women was lower in a study from Korea 24 than in different studies from the United States and Europe. 7,22,26 These differences are more likely explained by differences in techniques rather than ethnic differences because anal pressures in healthy Asian volunteers 23,25 were similar to those from a group that included participants from Western countries. 7,22,26 The HR-ARM system (Sandhill Scientific) used in the Korean study 24 averages anal pressures across radial sensors at any level of the catheter.…”

“…7,22,26 These differences are more likely explained by differences in techniques rather than ethnic differences because anal pressures in healthy Asian volunteers 23,25 were similar to those from a group that included participants from Western countries. 7,22,26 The HR-ARM system (Sandhill Scientific) used in the Korean study 24 averages anal pressures across radial sensors at any level of the catheter. This might explain why pressures measured with the Sandhill HR-ARM catheter are lower than those measured with the eSleeve program (Given Imaging HR-ARM and HD-ARM).…”

“…7,[22][23][24][25][26][27] However, because the sample size in these studies was relatively small, additional studies are necessary to more precisely define the normal range for anorectal pressures. The interpretation of findings will rely on studies conducted with HRM where available and supplemented by data from studies conducted with non-HRM only when necessary.…”

“…32 However, it should be noted that the normal range of anal pressures is relatively wide; for example, from 33-91 mmHg among women aged greater than 50 years in 1 study with HRM. 22 Length of the high-pressure zone This is automatically determined by the software. For the Sierra HRM system, the length of the high-pressure zone (HPZ) is the length of the average pressure profile in the resting pressure frame defined as {rectal pressure + [(anal resting pressure − rectal pressure) × 0.25]}.…”